This invention relates to printers, and more particularly to printer drivers having filters that are both operating system-independent and printer-independent.
Printers have become an indispensable peripheral component for use with computers. Generally, data that is to be printed by an application is transferred to a xe2x80x9cprinter driverxe2x80x9d via an operating system. The printer driver is a software module that translates the data to be printed into a format that is understandable by the printer. Various additional formatting options may also be provided by the driver, such as adding water marks, re-sizing the data for a page (e.g., expanding or shrinking the data to fit on a particular number of pages), etc.
Printer drivers are typically written by the printer manufacturer and are designed to work with a particular printer as well as a particular operating system. Different drivers generally need to be written for each possible printer/operating system combination that the printer manufacturer wants to support. Maintaining separate printer drivers for each printer/operating system combination is a particularly burdensome task for the printer manufacturer. Furthermore, given that many of the same formatting options are provided by each of the drivers (e.g., adding water marks), maintaining separate printer drivers for each printer/operating system combination causes repetitive efforts as each formatting option is designed into each of the printer/operating system combinations.
Additionally, situations can arise where it is desirable to alter the programming of a printer driver. Examples of such situations include the need to change the code for one of the formatting options in order to fix a bug or other error in the code, to provide increased functionality, etc. However, changing the programming of any one of the formatting options requires re-compiling the entire printer driver, including those parts of the driver not affected by the change in formatting option. Additionally, if the formatting option is changed after the printer driver has been distributed to the public, then the entire re-compiled driver must be re-distributed and re-installed by the public.
This invention addresses these disadvantages, providing an improved way to generate printer drivers.
A printer driver in accordance with the invention uses filters that are operating system-independent and printer-independent. Print requests and corresponding print data are received by the printer driver and converted into an internal representation that is both operating system-independent and printer-independent. The data to be printed is then passed through a print pipeline where one or more of a plurality of print filters are applied to the data. As a final stage in the print pipeline, the data is converted to a printer-dependent representation.
According to one aspect of the invention, a filter list is maintained by the printer driver. The filter list identifies the print filters that are part of the print pipeline and also identifies the order in which the filters are to be applied to the data to be printed.
According to another aspect of the invention, one or more of the plurality of filters used in the print pipeline are stored in a dynamic link library (DLL). The filters in the DLL are bound to the printer driver at run-time, allowing the filters in the DLL to be generated (and/or changed) after the printer driver is compiled.